Electrochemical Air Breathing Voltage Supply and Power Source Having in-situ Neutral-pH Electrolyte

Abstract

The invention is a metal air fuel cell consisting of a cathode contained in a housing, the housing having an air passage through which air (O 2 gas) can pass to the cathode. The air passage is sealed by a gas (i.e. O 2 ) permeable membrane. The fuel cell further includes an anode made of a metal selected from the group of metals including aluminum, zinc, magnesium, and alloys thereof. The cathode and anode are electrochemically coupled by an electrolyte such that the cathode and anode are capable of electrochemically reacting to consume O 2 gas at a volume rate of V when producing a desired electrical current of I. The gas permeable membrane has a gas permeability rate and a surface area through which O 2 gas can pass through the gas permeable membrane to the cathode, the surface area and the gas permeability rate of the gas permeable membrane selected to permit O 2 gas to pass through the membrane at a rate V m substantially equal to V at the desired current I. The permeable membrane is configured to reduce the transfer of water vapor through the membrane.

1 . A metal air fuel cell comprising:
 a housing;   a cathode;   the housing having an air passage through which air can pass to the cathode, the air passage being sealed by a gas permeable membrane;   an anode made of a metal selected from the group comprising aluminum, zinc, magnesium, and alloys thereof;   the cathode and anode being electrochemically coupled by an electrolyte such that the cathode and anode are capable of electrochemically reacting to consume O 2  gas at a volume rate of V when producing a desired electrical current of I, and   the gas permeable membrane having a gas permeability rate and a surface area through which O 2  gas can pass through the gas permeable membrane to the cathode, the surface area and the gas permeability rate of the gas permeable membrane selected to permit O 2  gas to pass through the membrane at a rate V m  substantially equal to V at the desired current I.   
   
   
       2 . The metal air fuel cell of  claim 1  wherein the gas permeable membrane is configured to restrict the passage of water vapor through the gas permeable membrane. 
   
   
       3 . The metal air fuel cell of  claim 2  wherein the gas permeable membrane is hydrophobic. 
   
   
       4 . The metal air fuel cell of  claim 1  wherein the electrolyte is carried in a gel matrix having a plurality of micro-cells. 
   
   
       5 . The metal air fuel cell of  claim 4  wherein the gel matrix is formed from starch and glycerin. 
   
   
       6 . The metal air fuel cell of  claim 5  wherein the electrolyte comprises a substantially pH neutral gelled solution of saline at a concentration of about 5% by weight, starch at a concentration of about 2% to about 3% by weight, alcohol at a concentration of about 7.5% by weight and glycerin at a concentration of about 7.5% by weight. 
   
   
       7 . The metal air fuel cell of  claim 6  wherein the electrolyte is contained in a porous cellulose layer. 
   
   
       8 . The metal air fuel cell of  claim 1  wherein the cathode comprises a three layered cathode having a substantially gas impermeable hydrophilic layer, a gas permeable hydrophobic layer containing a current collector mesh and a transition layer between the hydrophobic and hydrophilic layers, the transition layer being progressively more hydrophilic from the hydrophobic layer towards the hydrophilic layer. 
   
   
       9 . A metal air fuel cell comprising:
 a housing;   a first pair of flat cathodes contained in a parallel orientation within the housing;   the housing having first air passages through which air can pass to the first pair of flat cathodes;   a first pair of flat anodes positioned between the first pair of flat cathodes and extending parallel thereto, the anodes being made of a metal selected from the group comprising aluminum, zinc, magnesium, and alloys thereof;   a second pair of flat cathodes positioned between the first pair of flat anodes and extending substantially parallel thereto, the second pair of flat cathodes enclosing a second air passage, the second air passage being coupled to the housing to permit air to pass to the second pair of cathode plates;   the first and second pairs of cathode plates being electrochemically coupled by an electrolyte to the first pair of anode plates, the electrolyte selected such that the anode plates and the cathode plates are capable of electrochemically reacting to consume O 2  gas to produce a desired electrical current.   
   
   
       10 . The metal-air fuel cell of  claim 9  wherein the first pair of cathode plates are made from a first single elongated flat cathode which has been folded into first parallel portions and wherein the first anode plates are made from a single elongated flat anode which has been folded into second parallel portions and wherein the second pair of cathode plates are made from a second single elongated flat cathode which has been folded into third parallel portions. 
   
   
       11 . The metal-air fuel cell of  claim 10  wherein the first single elongated flat cathode is corrugated to form a plurality of first parallel portions each having a parallel pair of flat cathode plates and wherein the single elongated flat anode is corrugated to form a plurality of second parallel portions each having a parallel pair of flat anode plates and wherein the second elongated flat cathode is corrugated to form a plurality of third parallel portions each having a parallel pair of flat cathode plates separated by a second air passage, the first and second single elongated flat cathodes being aligned with each other and with the first single elongated flat anode such that the first, second and third parallel portions are aligned with each other each third parallel portion is nestled within a corresponding second parallel portion which is in turn nestled within a corresponding first parallel portion. 
   
   
       12 . The metal-air fuel cell of  claim 11  wherein a plurality of first air passages are formed between adjacent first parallel portions, the plurality of first air passages being coupled to the housing such that air can pass to the parallel pairs of flat cathode plates formed in the first single elongated flat cathode and wherein the housing is further configured to couple to the second air passages such that air can pass to the parallel pairs of flat cathode plates formed in the second single elongated flat cathode. 
   
   
       13 . The metal-air fuel cell of  claim 9  wherein the first and second pairs of cathode plates electrochemically react with the anode to consume O 2  gas at a rate of V when producing a desired electrical current of I, and wherein the first and second air passages are sealed by a gas permeable membranes, the gas permeable membranes each having an O 2  gas permeability rate and a surface area through which O 2  can pass to the first and second cathodes, the surface area and the gas permeability rate of the membranes selected to permit O 2  gas to pass through the membranes at a rate V m  substantially equal to V at the desired current I. 
   
   
       14 . The metal-air fuel cell of  claim 9  wherein the electrolyte is carried in a gel matrix having a plurality of micro-cells. 
   
   
       15 . The metal air fuel cell of  claim 14  wherein the gel matrix is formed from starch and glycerin. 
   
   
       16 . The metal air fuel cell of  claim 15  wherein the electrolyte comprises a gelled solution of saline at a concentration of about 5% by weight, starch at a concentration of about 2% to about 3% by weight, alcohol at a concentration of about 7.5% by weight and glycerin at a concentration of about 7.5% by weight, the electrolyte being soaked into a porous cellulose layer. 
   
   
       17 . The metal air fuel cell of  claim 9  wherein the first, second, third and fourth cathodes each comprise a three layered cathode having a substantially gas impermeable hydrophilic layer, a gas permeable hydrophobic layer containing a current collector mesh and a transition layer between the hydrophobic and hydrophilic layers, the transition layer being progressively more hydrophilic from the hydrophobic layer towards the hydrophilic layer. 
   
   
       18 . The metal-air fuel cell of  claim 9  wherein the metal forming the anode comprises a metal having an additive selected from the group comprising Ga, In, Sn, Cd and Pb. 
   
   
       19 . The metal-air fuel cell of  claim 18  wherein the anode is made of an Al—In alloy formed from Aluminum having 99.95% purity and In in about 0.2 to 0.6% by weight. 
   
   
       20 . The metal-air fuel cell of  claim 19  wherein the anode has a homogeneous crystal structure. 
   
   
       21 . The metal-air fuel cell of  claim 20  wherein the Al—In alloy is first melted at 660° C. and then cooled into alloy plates in non-equilibrium, homogeneous crystal-forming conditions and then the alloy plates are cold rolled to form the anode. 
   
   
       22 . A method of forming an anode for use with the metal-air fuel cell defined in  claims 1  and  9  comprising:
 melting a first metal selected from the group comprising aluminum, zinc, magnesium and alloys thereof with an additive selected from the group comprising Ga, In, Sn, Cd, Pb to a first temperature to form a melt, the first temperature selected to be just above the melting point of the selected metals and additives;   cooling the melt under non-equilibrium, homogeneous crystal forming conditions to form an alloy plate with a homogeneous crystal structure, and then cold working the alloy plate to a desired thickness.